The present invention relates generally to the imprintation of decorative or informative indicia on articles, and more particularly relates to tilt screen type screen printing machines used for such imprintation purposes.
Tilt screen type screen printing machines are well known devices and are commonly used to print decorative and informative indicia on a wide variety of both flat and round articles such as paper stock, tee shirts, cans, bottles, cups and the like. Conventional screen printing machines typically comprise a base frame structure upon which a vertically spaced pair of horizontal upper and lower support rods are carried. The upper and lower rods are respectively utilized to support a squeegee carrying structure and a printing screen support frame structure, each of which is translatable along the length of its associated support rod and is pivotable about the rod axis.
The squeegee carrying and printing screen support frame structures of these conventional machines are typically anchored to carrier members which are slidably and rotatably mounted on the support rods. This connection method permits the desired horizontal translation and vertical pivoting of both the squeegee carrying structure and the printing screen support frame structure. When either structure is vertically pivoted its carrier member, in its entirety, is also pivoted about its associated support rod.
To use the machine, a printing screen is suitably clamped to the screen support frame structure and both the squeegee carrying structure and the screen are upwardly pivoted. The article to be imprinted is supported on a lift table structure beneath the screen and squeegee, and the screen and squeegee are lowered to their operative positions directly above the article. A relative horizontal movement is then created between the screen and squeegee to cause the squeegee to drive ink (previously deposited on the upper side of the screen) downwardly through the screen and onto the supported article to imprint thereon predetermined indicia formed on the screen. The screen and squeegee are then pivoted upwardly away from the now imprinted article, the imprinted article is removed from the lift table and replaced with another article, and the imprintation process is repeated.
In the case of flat articles, such as paper stock or tee shirts, the lowered printing screen is held stationary while the squeegee is horizontally moved across the upper side surface of the screen. When round articles such as bottles or cans are being imprinted, the squeegee is held stationary while the screen is horizontally translated and the article is simultaneously rotated.
As is well known in the printing art, conventional tilt screen type printing machines of this general type are subject to a variety of problems, limitations and disadvantages. For example, when round articles are being imprinted it is often necessary to maintain a precise correlation between the horizontal motion of the screen and the rotation of the article to assure a correct circumferential positioning of the imprintation on the round article being decorated. For example, when cups are being imprinted it is of course desirable that the resulting imprinted indicia on every cup is positionally related to its handle in the same manner.
For each successive cup this requires that, at the beginning of the horizontal screen stroke, the cup handle be rotationally oriented at a starting position identical to the starting position of every other cup to be imprinted with the same screen indicia. In the past, this necessary screen/article motion correlation has essentially prevented the effective use of a tilt screen type screen printing machine to imprint round articles.
Another problem heretofore associated with conventional tilt screen printing machines has been the difficulty in using power drive mechanisms to horizontally translate the squeegee support and printing screen support frame structures back and forth along their support rods. This problem arises due to the fact that as the squeegee support and printing screen support frame structures are pivoted their carriers are also pivoted about their associated support rods. This resultant pivoting of the carrier members has heretofore required the use of a fairly complex and expensive translational drive system to compensate for such pivoting.
A further limitation of conventional screen printing machines of this type is that they are typically only capable of performing screen printing processes. In order to carry out other imprintation tasks such as, for example, pad transfer printing, it has heretofore been necessary to use a separate machine or system. Additionally, from a somewhat broader perspective, conventional tilt screen type screen printing machines have tended to be relatively large, complex and expensive.
In view of the foregoing, it is accordingly an object of the present invention to provide an improved tilt screen type screen printing machine which eliminates or minimizes the above-mentioned and other problems, limitations and disadvantages heretofore associated with conventional screen printing machines of the general type described.